The sensation of different colours are produced by combinations of cones and their photopigments. If cones are stimulated equally, the sensation of white light is produced.(b) The cristae and maculae found in inner ear help to maintain body balance.The retina is the innermost layer of eye ball. The iris has sphincters and dilators which are smooth muscles and these regulate with amount of light entering ball by varying size of pupil.(ii) The contraction of sphincter muscles make pupil smaller in bright light. Hence less light enters eye.(iii) Contraction of dilater muscles widens pupils indim light. More light goes into eye and falls on the retina.